NASA hopes to avoid more hydrogen leaks during 2nd Artemis 2 rocket fueling test today: Watch live

NASA's Artemis II Live Views from Kennedy Space Center - YouTube

The second prelaunch test campaign for NASA's Artemis 2 moon rocket is underway, and one of its most critical operations will happen today (Feb. 19).

NASA's Space Launch System (SLS) rocket entered hour 36 of its approximately 50-hour-long wet dress rehearsal (WDR) this morning, as Artemis 2 mission managers began final preparations for the fueling portion of the launch countdown simulation. It's the second such test the Artemis 2 SLS has had to undergo, after liquid hydrogen (LH2) leaks during its first WDR on Feb. 2 ended that campaign prematurely.

Ground teams at NASA's Kennedy Space Center (KSC) in Florida are working toward a simulated liftoff this evening at 8:30 p.m. EST (0130 GMT on Feb. 20), with a window that extends as late as 12:30 a.m. EST (0530 GMT) on Friday (Feb. 20). Between then and now, NASA will have to successfully load SLS with about 730,000 gallons (2.73 million liters) of LH2 and liquid oxygen (LOX). Such work is designed to demonstrate the rocket's readiness for an actual liftoff with a crew of astronauts on a mission around the moon, which, if everything goes smoothly, could launch as soon as March 6.

a tall orange rocket stands in the distance on the left, with a large white fuel tank in the foreground on the right. — NASA’s Artemis 2 SLS (Space Launch System) rocket with the Orion spacecraft and launch abort system atop stands vertical in the background with a 1.4-million-gallon, 83-foot-wide, liquid hydrogen sphere in the foreground at Launch Complex 39B at NASA’s Kennedy Space Center in Florida on Feb. 10, 2026. (Image credit: NASA/Ben Smegelsky)

Artemis 2 SLS wet dress rehearsal latest news: NASA continues 2nd Artemis rocket fueling test

NASA is providing a commentary-free, 24-hour livestream of SLS during the WDR, which can be viewed here on Space.com as well as on YouTube. The agency said that it will also air a separate stream featuring important WDR activities; Space.com will simulcast that feed, if it's made available.

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A "go/no-go" poll to begin tanking is expected today at around 9:50 a.m. EST (1450 GMT), with the core stage's LH2 "slow fill" beginning about an hour later. Fueling operations, including vehicle stage cool-downs, are scheduled to last from 9:50 a.m. EST (1450 GMT) until 3:30 p.m. EST (2030 GMT), when a planned countdown hold will be implemented as the LH2 and LOX lines enter a replenishing phase.

The two-day-long WDR is meant to put Artemis 2 and ground teams through their paces and ensure that all equipment, personnel and procedures are appropriately in place and ready to launch astronauts to the moon. Artemis 2 is the second mission of NASA's Artemis program and the first to fly with a crew aboard the Orion capsule.

WDR — Wet Dress Rehearsal

SLS — Space Launch System

LOX — Liquid Oxygen

LH2 — Liquid Hydrogen

KSC — Kennedy Space Center

Once cleared for launch, Orion will carry NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and the Canadian Space Agency's Jeremy Hansen on a 10-day trip around the moon and back to Earth on the first crewed lunar voyage since the Apollo missions ended in 1972.

Throughout testing today, engineers at KSC will be keeping a close eye on a section of the SLS mobile launch platform that connects to the bottom of the rocket, known as the tail service mast, where umbilical lines run to supply fuel and other resources to the rocket.

The tail service mast "quick disconnect," where it interfaces with the rocket, was the site of LH2 leaks during the first Artemis 2 WDR earlier this month, and is also the same component that plagued the rocket with leaks during the Artemis 1 launch campaign in 2022. Those issues resulted in three rollbacks of SLS to the Vehicle Assembly Building at KSC that year — a repeat of which NASA is hoping to avoid this time around. Officials say that lessons learned from Artemis 1 have resulted in hardware modifications and improved procedures, which will allow them to better manage thermal conditions during cryogenic fueling and (hopefully) avoid similar leaks.

Should mission teams reach the other side of today's tanking operations, the wet dress rehearsal will enter a series of countdown milestones to simulate a variety of launch scenarios, including holds on the clock, launch scrub conditions and detanking. A successful WDR could put Artemis 2 on track to lift off as early as March 6, though NASA officials say they are waiting to review WDR data before setting an official target date.

The March window for Artemis 2 extends from March 6-9, and includes March 11. A subsequent window opens in the beginning of April. Further opportunities fluctuate around the starts and ends of each month thereafter, as they correspond with the phase of the moon for optimal launch conditions.

A full timeline of today's procedures, which work toward a T-0 of 8:30 p.m. EST (0130 GMT, Feb. 20), is as follows, courtesy of NASA:

L-16 hours and counting (around 4:40 a.m. EST)
L-15H30M – L-13H30M: All non-essential personnel leave Launch Complex 39B
L-14H15M – L-12H05M: Air-to-gaseous nitrogen (GN2) changeover and vehicle
cavity inerting
L-13H45M – L-12H15M: Ground Launch Sequencer (GLS) activation
L-12 hours and counting
L-12H35M – L-9H50M: 2-hour 45-minute built in countdown hold begins
L-10H50M: Launch team decides if they are “go” or “no-go” to begin tanking the
rocket
L-10H50M – L-9H35M: Orion cold soak
L-10H40M – L-10H325M: Core stage LOX transfer line chilldown
L-10H40M – L-9H55M: Core stage LH2 chilldown
L-10H20M – L-9H40M: Core stage LOX main propulsion system chilldown
L-10 hours and counting
L-9H55M – L-9:35H: Core stage LH2 slow fill start
L-9H50M: Resume T-Clock from T-8H10M
L-9H45M – L-9H30M: Core stage LOX slow fill
L-9H35M – L-8H10M: Core stage LH2 fast fill
L-9H30M – L-7H10M: Core stage LOX fast fill
L-9H15M – L-8H45M: ICPS LH2 chilldown
L-8H45M – L-7H55M: ICPS LH2 fast fill start
L-8H10M – L-7H10M: ICPS LOX main propulsion system chilldown
L-8H10M – L-8H: Core stage LH2 topping
L-8H – terminal count: Core stage LH2 replenish
L-7H55M – L-7H40M: ICPS LH2 vent and relief test
L-7H40M – L-7H25M: ICPS LH2 tank topping start
L-7H25M – terminal count: ICPS LH2 replenish
L-6H45M – L-6H15M: Orion communications system activated (RF to mission
control)
L-6H40M – L-6H05M: Core stage LOX topping
L-6H30M – L-5H45M: ICPS LOX fast fill
L-6H05M – terminal count: Core stage LOX replenish
L-6 hours and counting
L-5H45M – L-5H30M: ICPS LOX vent and relief test
L-5H30M – L-5H10M: ICPS LOX topping
L-5H40M: Stage pad rescue
L-5H40M: Closeout crew assemble
L-5H10M – terminal count: ICPS LOX replenish
L-5H10M: All stages replenish
L-5H10M: Start 1-hour 10-minute built in hold
L-4H40M-L-4H25M: Closeout crew to white room
L-4H30M – L-4H20M: Crew module hatch preps and closure
L-4H20M – L-3H20M: Counterbalance mechanism hatch sealpress decay
checks
L-3H20M – L-2H40M: Crew Module hatch service panel install/closeouts
L-2H50M – L2H25M: Launch Abort System (LAS) Hatch closure for flight
L-1H10M: Launch Director brief – Flight vehicle/TPS Scan results with CICE
L-1H45M – L-1H40M: Closeout crew departs Launch Complex 39B
L-40 minutes and holding
L-40M: Built in 30-minute countdown hold begins
L-25 minutes and holding
L-25M: Transition team to Orion to Earth communication loop following final NTD
briefing
L-16M: The launch director polls the team to ensure they are “go” for launch
T-10 minutes and counting
T-10M: Ground Launch Sequencer (GLS) initiates terminal count
T-8M: Crew Access Arm retract
T-6M: GLS go for core stage tank pressurization
T-6M: Orion set to internal power
T-5M57S: Core stage LH2 terminate replenish
T-4M: GLS is go for core stage auxiliary power unit (APU) start
T-4M: Core Stage APU starts
T-4M: Core stage LOX terminate replenish
T-3M30S: ICPS LOX terminate replenish
T-3M10S: GLS is go for purge sequence 4
T-2M02S: ICPS switches to internal battery power
T-2M: Booster switches to internal batter power
T-1M30S: Hold for three minutes to verify core stage certification hold time
T-1M30S: Core stage switches to internal power
T-1M20S: ICPS enters terminal countdown mode
T-50S: ICPS LH2 terminate replenish
T-33S: GLS sends “go for automated launch sequencer” command
T-33S: GLS Cutoff/Recycle

Josh Dinner is the Staff Writer for Spaceflight at Space.com. He is a writer and photographer with a passion for science and space exploration, and has been working the space beat since 2016. Josh has covered the evolution of NASA's commercial spaceflight partnerships and crewed missions from the Space Coast, as well as NASA science missions and more. He also enjoys building 1:144-scale model rockets and human-flown spacecraft. Find some of Josh's launch photography on Instagram and his website, and follow him on X, where he mostly posts in haiku.

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